452 PHYSIOLOGY CHAP. 



distributed to the convoluted tubules, where they terminate in 

 the form of spherical dilatations or delicate fibrils, which penetrate 

 the basement membrane, and are presumably in connection with 

 the cement substance of the epithelial cells (Fig. 122, 3, 4> &) 



These anatomical observations of Berkley were confirmed and 

 amplified later on by Azoulay (1894) and Pensa (1896), and more 

 particularly by the painstaking researches of T. D'Evant (1899), 

 who described four different kinds of nerve-endings in the kidney : 

 (a) the terminations in the walls of the vessels ; (&) those of the 

 Malpighian glomeruli ; (c) those of the convoluted tubules ; (d) 

 the free nerve - endings in the glandular parenchyma, which, 

 according to this author, have a centripetal function. 



Evidently the function of these nerve fibrils can only be 

 trophic or secretory, and, is quite distinct from that of the vascular 

 branches. 



As we have stated, however, no physiological experiment has 

 yet given indisputable evidence of the existence of secretory nerves 

 to the kidney. In 1835 Cl. Bernard affirmed that puncture of 

 the floor of the 4th ventricle produced polyuria, which is frequently, 

 but not invariably, accompanied by glycosuria. He explained the 

 different effects of puncture by the varying position of the 

 lesions. The point at which hepatic secretion of sugar is excited 

 lies rather deeper than that by which renal secretion of urine is 

 excited, but they are so close together that both are frequently 

 involved by the puncture, so that polyuria and glycosuria result. 



Eckhard on repeating the experiments was unable to 

 accept this interpretation. In rabbits he found that simple 

 hydruria occurred very seldom. In these animals, on the other 

 hand, hydruria and glycosuria can be produced by mechanical, 

 electrical, and chemical stimulation of that part of the vermis of 

 the cerebellum which covers the rhomboidal sinus; if the nerves 

 to the liver had been divided previous to excitation simple hydruria 

 resulted. 



The clinical phenomenon of polyuria or hydruria (also known 

 as diabetes insipidus) shows the possibility of increased urinary 

 secretion independent of the internal secretion of the liver. 

 Diabetes insipidus has been observed in cases of inflammation and 

 tumours of the medulla oblongata, and in cerebral disturbance, also 

 as an after-effect in attacks of epilepsy and hysteria (Ebstein). 



The polyuria due to puncture is not caused by rise of arterial 

 pressure, since this does not vary, or falls slightly; it might 

 therefore arise from excitation of renal secretory fibres, as con- 

 jectured by Eckhard. But it is more probable, as Starling holds, 

 that it depends on the excitation of renal vaso-dilator fibres. 



After division of the splanchnic nerve, the flow of urine at 

 once increases in the kidney of the side operated on, but this 

 increased secretion lasts a long time (3-4 hours), so that it cannot 



